My 347 runs fine with the 24lb injectors in it, i've checked the plugs there an alright colour but i want them darker, but when i run the 30's it runs like crap at idle, it surges and sounds like its puken. Should i crank up the pressure on the 24's or drop the pressure on the 30's?, i'm at 38psi with the 24's right now at idle vacuum connected. Please only respond if you have done this before and what pressures you ran, no guesses please, thanks....Keith
24#r's not enough 30#r's to much which one's to play with?
- Thread starter keith black
- Start date
From what I've read, the ecu working with readings from the 02's will keep the plugs quite clean during normal driving. It's only in WOT that fuel pressure has much of an effect on mixture. (Other than tuning the ecu tables etc).
In building my 351 on a very tight budget, I found an early 70mm Ford air meter that was sold by Ford to be used with 30 lb injectors on a stock 5.0 ecu. I know 30's are too big for my combo, but that's the best deal I could find at the time.
I later had a dyno tune mostly to check for air fuel ratio and to see what effect more advanced timing would have. The dyno guy strongly suggested I install a Kirban adjustable regular and turn it down to mid 30's before the session, which I did.
The 2 dyno runs showed an air fuel ratio real close to optimum. My plugs are real clean indicating the ecu is working fine during normal daily driving. It does lope just a bit at 800 idle but that probly is partly due to the cam & 1.72 rockers. Not to say a properly set up 24 lb system might not idle a little better. However, it runs just fine, has good power for what it is, and I get what I consider to be excellent road mileage.
I recently picked up a lo miles used 75mm Pro M calib'd for 24's and a set of good used inj's which I'll stick in and try "some day" when I get the time just to see if it makes any difference.
After I put in the regulator and turned the pressure down, my tail pipes are running much cleaner - less soot - and my plugs are also cleaner.
Also from what I've read, the smaller injectors are better & more tuneable for street driving as long as you don't go over the 85 or 95% of duty cycle during WOT, so I would suspect your 24's might be a little better for your combo.
In building my 351 on a very tight budget, I found an early 70mm Ford air meter that was sold by Ford to be used with 30 lb injectors on a stock 5.0 ecu. I know 30's are too big for my combo, but that's the best deal I could find at the time.
I later had a dyno tune mostly to check for air fuel ratio and to see what effect more advanced timing would have. The dyno guy strongly suggested I install a Kirban adjustable regular and turn it down to mid 30's before the session, which I did.
The 2 dyno runs showed an air fuel ratio real close to optimum. My plugs are real clean indicating the ecu is working fine during normal daily driving. It does lope just a bit at 800 idle but that probly is partly due to the cam & 1.72 rockers. Not to say a properly set up 24 lb system might not idle a little better. However, it runs just fine, has good power for what it is, and I get what I consider to be excellent road mileage.
I recently picked up a lo miles used 75mm Pro M calib'd for 24's and a set of good used inj's which I'll stick in and try "some day" when I get the time just to see if it makes any difference.
After I put in the regulator and turned the pressure down, my tail pipes are running much cleaner - less soot - and my plugs are also cleaner.
Also from what I've read, the smaller injectors are better & more tuneable for street driving as long as you don't go over the 85 or 95% of duty cycle during WOT, so I would suspect your 24's might be a little better for your combo.
The following examples are only for naturally aspirated engines.
Injector HP ratings: divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle.
Example:
19/.5 = 38, 38 x 8 = 304
24/.5 = 48, 48 x 8 = 384
30/.5 = 60, 60 x 8 = 480
The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85 (cheat on the math and use .588 instead of .5 and you don’t have to multiply the end result by.85)
Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.
Use the SOP meter...
Get one of your buddies to ride along with you. Find a level stretch of road where you can do some testing. Don't choose a speed range that will make you shift gears, the shift quality & speed will affect your results. Use 2nd or 3rd gear and do a run from 2000 RPM to 5800 RPM. Call out the RPM as it increases and have you buddy record it and the elapsed time. If you have one of those cheap digital watches like I do, a stop watch is built in. Start the fuel pressure at 36 PSI, vacuum off and make a run. Turn it up to 37 and make another. Be sure to reconnect the vacuum every time you set the pressure. Keep turning up the pressure and making runs until you notice a drop off in time. If your bud was careful to record the results, you'll have a nice chart to use to find the optimum pressure.
Injector HP ratings: divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle.
Example:
19/.5 = 38, 38 x 8 = 304
24/.5 = 48, 48 x 8 = 384
30/.5 = 60, 60 x 8 = 480
The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85 (cheat on the math and use .588 instead of .5 and you don’t have to multiply the end result by.85)
Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.
Use the SOP meter...
Get one of your buddies to ride along with you. Find a level stretch of road where you can do some testing. Don't choose a speed range that will make you shift gears, the shift quality & speed will affect your results. Use 2nd or 3rd gear and do a run from 2000 RPM to 5800 RPM. Call out the RPM as it increases and have you buddy record it and the elapsed time. If you have one of those cheap digital watches like I do, a stop watch is built in. Start the fuel pressure at 36 PSI, vacuum off and make a run. Turn it up to 37 and make another. Be sure to reconnect the vacuum every time you set the pressure. Keep turning up the pressure and making runs until you notice a drop off in time. If your bud was careful to record the results, you'll have a nice chart to use to find the optimum pressure.
RaceDvr50
New Member
Yeah like he said, you can effectively get 30 out of your 24's if you up the pressure but you can't get 27 out of your 30's so play with the lower pound injectors first. 38psi is a little low for 24's anyway, Ford recommends that you run 24's at 40 psi or above for proper atomization / spray pattern.
Grn92LX said:I don't care about your engine. Don't forget Ed Curtis said for you to get 30's too
I don't care about yours...lol. 115mph...with a track setup. Ouch
Them gears will give you a 5mph gain...lol. Um, not.Yep, but, with a tune on a dyno. You like your little PMS...because you have PMS much of the time if someone doesn't like your over the hill part selection..."
"5spd GT said:I don't care about yours...lol. 115mph...with a track setup. Ouch
Yep, but, with a tune on a dyno. You like your little PMS...because you have PMS much of the time if someone doesn't like your over the hill part selection..."
This is comming from someone who just put a $2k shortblock back in his car and went NO faster HAHAHAHA!!!!!
Don't worry about what my 4.30's will give me. When I get time to get to the track i'll see what they give me. An extra 1000 rpm's in the meat of my powerband has to do something "
"Grn92LX said:This is comming from someone who just put a $2k shortblock back in his car and went NO faster HAHAHAHA!!!!!
Don't worry about what my 4.30's will give me. When I get time to get to the track i'll see what they give me. An extra 1000 rpm's in the meat of my powerband has to do something "
You obviously aren't very wise. Did I get my shortblock for more power. Obviously not, I got it for reliability...look at the cubes...it will fall together for you, if you pay attention. I didn't buy a 2k shortblock.
I also added longtubes and went "no faster"...ouch on you
5mph...funny.
So how is your PMS?
You told me in another thread you paid about $2k for your shortblock @ kieth craft, don't deny it.
My Anderson Ford Motorsport PMS is great! One of the best things i've bought for the car. Very versatile unit and its done more than I could ever ask it to.
Next time I hit the track (hopefully soon before it gets too hot) I will see what the gears, better tuning and UPR control arms do for me. This will be pass #4 for the combo so I don't have too much seat time with it. I need a dr gas 3" X pipe to finish my little street combo.
My Anderson Ford Motorsport PMS is great! One of the best things i've bought for the car. Very versatile unit and its done more than I could ever ask it to.
Next time I hit the track (hopefully soon before it gets too hot) I will see what the gears, better tuning and UPR control arms do for me. This will be pass #4 for the combo so I don't have too much seat time with it. I need a dr gas 3" X pipe to finish my little street combo.
RaceDvr50
New Member
Grn92LX said:
Of course stock fuel pressure is what we want because none of us could ever handle the complexities of adjusting fuel pressures to make our fuel injectors flow the poundage we want. Just use stock fuel pressure and you have only the choices of 19lb 24lb 30lb etc. Don't forget to buy that $100 dollar adjustable fuel pressure regulator and set it to stock fuel pressure because it's not that you want to use it, it just looks good sitting there.
$uperstang
New Member
I use 24's set at 44 PSI to give you an idea. I am guessing yours ran like crap with the 30's because you forgot to re-calibrate your MAFS? I would think with your set-up you should go with 36's.
thanks again for the soap opera in here, i have both calibration tubes for my C&L 24 and 30. i since have set my regulator to 44 also and i runs excellent. Why 36lb injectors when i can crank out my 24's to my 400hp setup??? Read the chart up there sounds right to me, but i do need to get my ecu burnt on a dyno.
Grn92LX said:
I didn't buy a shortblock. Shortblock has oil pump, oil pan, etc. on it. Sorry, you lose.
Up where you live, it doesn't get hot, it gets perfect. It won't effect your times, not 5mph worth
You have plenty of seat time when you drive it. I know you don't put around. Whether on a two-lane road or a two-lane drag strip...you'll be driving the same.
RaceDvr50
New Member
keith black said:
You are welcome, glad we could help. Some people will never understand though bigger isn't better if it doesn't match your combo.
Similar threads
